Catalytic fragrance burners are used to disperse a fragrance in a room. Such burners include a ceramic stone which is impregnated with a suitable catalyst, such as platinum, palladium or lanthanum. An alcohol-based fuel is fed to the ceramic stone using a wick. The wick is arranged to hang within a fuel reservoir, in order to draw fuel to the ceramic stone. The burner is typically started by holding a naked flame to the ceramic stone. This causes the fuel to catch alight, which produces a relatively high (perhaps 4 to 6 inches) naked flame. As the ceramic stone heats up, catalytic combustion occurs in and around the stone. After around three minutes or so, the ceramic stone reaches an operating temperature of around 330° C., after which the naked flame can be extinguished. Catalytic combustion continues in and around the stone, and the device continues to operate without a flame.
A typical catalytic fragrance burner 100 is shown in cross-section in FIG. 1. The burner 100 includes an outer ceramic stone 102 and an inner ceramic stone 104. The outer stone 102 is coated with a catalyst coating 106 and the inner stone 104 is coated with catalyst coating 108, both of which are made from the same catalyst. The outer stone 106 includes a wick receiving portion 110. The fragrance burner 100 also includes a wick 112, which is a length of rope, formed in a loop so that both ends 114, 116 are located in the wick receiving portion 110. The burner 100 also includes a metal sheath 118, which fits around the outer stone 102. The metal sheath has an opening in its base having a diameter slightly narrower than the wick receiving portion, so as to lightly grip the wick 112. The burner 100 also includes a stone locking member 120, which clips into the metal sheath 118 and holds the inner stone 104 in position in the outer stone 102. The whole arrangement the sits on top of the neck of a fuel reservoir (not shown). Alternative designs include a one-piece ceramic stone, rather than two pieces of ceramic.
The above-described burner has a number of problems. Firstly, the ceramic stone has a fairly low porosity, and the pores are very small. As the fuel burns, incompletely combusted fragrance builds up, causing charring and causing the fuel to block the pores. The ceramic stone can not easily be cleaned, and as a result, the stone must be periodically replaced. Furthermore, when the device is started, it can take up to three minutes for the stone to get up to operating temperature, and an open flame is present during this time. This is both dangerous to the user, and time consuming. Furthermore, while heating up, the fuel is consumed at a much greater rate. Accordingly, there is a need for improved catalytic fragrance burners.
US Patent Application Publication No. US 2008/0090188A1 discloses one such example of an improved catalytic burner. The burner includes a non-porous substrate which is coated in a suitable catalyst. The wick is positioned in communication with the substrate. This device operates in the same way as the aforementioned prior art, but avoids the issue of pore clogging by using a non-porous catalyst substrate.
Some embodiments of the present invention provides an alternative catalytic fragrance burner assembly.